The present invention relates generally to septic systems, and more particularly to a leaching or drainage system for a septic system which uses lightweight, vacuum-molded polyethylene gallery structures to form the leaching field.
In terms of volume, most of the water used in households around the United States is employed to carry off wastes, most of these wastes being organic and inorganic solids. Larger volumes of water are used for washing dishes, bathing and flushing the toilet than for drinking, cooking, washing cars, etc.
In urban areas, wastes carried by water from kitchens, bathrooms and laundry rooms are collected in a sewer system and transported to central sewage treatment plants. In rural areas and in unsewered suburban residential areas, individual septic systems are used to treat household waste. There are millions of such septic systems presently in use and being built in the United States. If properly designed, installed and adequately maintained, such a septic system will serve a household satisfactorily to treat household wastes.
In use, a septic system will condition household water carrying dirt, detergents, discarded food scraps and body wastes so that water may be readily percolated into the sub-soil of the surrounding ground. A typical septic system is comprised of a rectangular precast cement septic tank buried in the ground having a leaching or drain field extending therefrom. Household wastes or sewage flows to the septic tank under the influence of gravity from the house via a sewer line or pipe. The septic tank is a large, watertight and lighttight container in which the organic solids found in the sewage are decomposed by natural bacterial processes. Once the sewage is introduced into the tank, large solid particles sink, forming a sludge at the bottom of the tank while smaller, lighter particles as well as oils and greases rise to the surface forming a scum layer over a volume of liquid material located between the sludge and scum layers. Bacteria and other organisms in the tank break down and reduce the volume of the solids and scum. The bacteria cannot attack some of the material introduced into the system such as stone particles, plastic, etc. and these materials must be removed from the tank by periodic tank cleanings.
An outlet pipe is provided in the tank permitting some of the liquid material known as effluent to flow via hydrostatic pressure from the tank. The effluent still contains some decomposed solids as well as bacteria, viruses, etc. found in the tank and flows into an adjoining leaching or drain field where it must be permitted to percolate through the surrounding ground.
The leaching field has traditionally been a trench in the ground about eighteen inches (18") wide filled with gravel. A four inch (4") perforated pipe is located in the trench surrounded by the gravel. Laid over the gravel and the pipe is a layer of tar paper, salt hay or woven plastic cloth with a layer of top soil placed thereover. The pipe is set at an appropriate pitch to permit a desired flow of the effluent therealong under the influence of gravity. In use, the effluent runs down the perforated pipe from one end of the pipe to the other and flows out the apertures therein into the surrounding gravel and eventually into the surrounding ground.
Another type of leaching field is formed of precast concrete galleries which create space underground within a gravel bed to increase the volume of the field. These galleries are made in different shapes (rectangular, triangular) and are ideal for situations where there is insufficient area for the traditional pipe and gravel systems.
Some of the drawbacks of the traditional septic systems are that the septic tanks and leaching galleries have been made from precast concrete and are extremely heavy requiring heavy construction equipment to put them in place. In the leaching fields, the gravel used in constructing them is difficult to work with and expensive. It also tends to settle and reduces the overall volume of the trench by as much as seventy five percent (75%).
The present invention is designed to overcome the limitations that are attendant upon the use of traditional septic systems, and toward this end, it contemplates the provision of a novel drainage system which can be easily transported to the installation location.
It is an object of the invention to provide a septic system which employs lightweight vacuum-molded polyethylene gallery structures to form the leaching or drain field.
It is also an object to provide such a drainage system which is relatively light weight compared to precast concrete systems.
A further object is to provide such a drainage system which may be readily and economically fabricated and will enjoy a long life in operation.